As you figured out, there would be many options to hide the "secret" calls. There is also no need to send these secret calls from all devices, it could be used only by a set of devices that are owned by "interesting" people. Assuming that is true, if a security researcher looked into things no longer proves anything.
Sure but there's probably provable ways to look for hidden stuff as well unless they are sending empty data.
You can do multiple runs of feeding pre-recorded messages into say multiple speakers and do the trial over many days. Then on a series of other speakers you can do a robust sequence of pre-recorded conversations followed by the same pre-recorded messages at the same time and then do statistical analysis on traffic volume.
I just presume these things are listening to everything and recording everything. I think that should be the general assumption if you bring essentially an "internet microphone machine" into your home.
If not by the company who sold it to you then by 3rd party hackers, clever app developers, or some other group. Every marketer wants to know what their customers are saying in the privacy of their own home.
As a tangent I've long wanted to have fun with this ... start a campaign to start collectively talking about a ridiculous product (say a vacuum cleaner with elephant ears that flap in proportion to the amount of dirt it picks up) in private conversations and see if a company releases it by listening in. "There's significant consumer demand for the dumbo-vac!"
> Sure but there's probably provable ways to look for hidden stuff as well unless they are sending empty data.
Isn't this equivalent to the halting problem? Even with source code, there is a chance the compiler was compromised. In practice, these devices are closed source, so you would need to verify all the possible code paths.
Moreover, we know that NSA coerced phone companies into exposing metadata. What is the probability NSA has not requested backdoors of Amazon, Google, and the like?
I don't think it is however there is an unprovable element here in that it's difficult to prove absence. However, depending on implementation it may not very difficult to demonstrate presence! If you run the basic tests and there's clearly a substantial difference between the two you're done. If there isn't, you need to dig deeper.
This is just the nature of indirect observation. People in the natural sciences deal with this problem all the time.
